1. Field of the Invention
The present invention relates to industrial image exposure devices that are used in lithographic processes to expose images onto substrates such as during the manufacture of liquid crystal display panels, semiconductor elements, etc.
2. Description of the Related Art
Industrial imaging devices such as image exposure devices are used to produce liquid crystal display panels, semiconductor elements, etc. For example, personal computers, laptop computers, word processors, televisions, and many other common devices include components that are manufactured, in part, by using image exposure devices. The manufacture of liquid crystal display panels, for example, has become increasingly reliant on image exposure devices and techniques. And, as such display panels have become more complex and intricate, so too have the manufacturing devices and processes associated with production of the same.
Liquid crystal display (LCD) panels often are produced, in part, by forming a conductive thin film electrode (e.g., of the Indium Tin Oxide (ITO) variety, etc.) on and affixing a liquid crystal molecular orientation element to a glass substrate and sealing that arrangement with a sealant or sealing member at the outer periphery of the substrate. Formation of ITO-type thin film electrodes and, in particular, complex LCD display segments have been achieved by imaging the same via lithographic image exposure devices and processes.
To perform such lithographic processes, a photolithographic image exposure device known as a xe2x80x9cstepperxe2x80x9d often is used. With a stepper, a desired pattern contained in a mask or on a reticle may be projected onto a substrate via a xe2x80x9cstep and repeatxe2x80x9d exposure method. Depending on the nature of the pattern to be exposed (e.g., the number and complexity of the display units to be exposed, etc.), other patterning devices and techniques have been used (e.g., scanning exposure devices using mirror projection aligners and systems, etc.).
Despite their widespread use to produce LCDs, etc., stepper throughput efficiency has become problematic. That is, as LCD elements have increased in complexity, the number of devices that can be made via step and repeat techniques has decreased. And, when using mirror projection type systems, etc., problems also have been realized in terms of manufacturing relatively large mirrors and assemblies to expose enlarged masks. As such, mirror-type systems have resulted in relatively large scanning devices and stepper units.
To address efficiency and size problems associated with prior stepper units, some have proposed scanning type exposure devices for relatively large circuit pattern masks. One such device is disclosed in Japanese Laid-Open Patent Publication Hei 7-57986 (U.S. Pat. No. 5,729,331). Such a scanning type exposure device uses plural projection optical systems to simultaneously scan a mask and a photosensitive substrate. As such, scanning type exposure devices of the type disclosed in the aforementioned Japanese patent publication have led to increased device throughput efficiency and decreased stepper size.
An exemplary scanning type exposure device (of the type illustrated in the aforementioned Japanese patent publication) is shown in drawing figure (FIG.) 1, which is attached to this document. In particular, the stepper unit exposure device shown in FIG. 1 includes a mask table 122 and a plate table 123 which are supported on a carriage 112. The carriage has a U-shaped cross-section. The mask and plate tables are supported opposite each other. A mask 113 and a plate 114 are respectively supported on tables 122 and 123. A mask-side reference mark plate 130 is fixed to the end of the mask table 122, and a plate-side reference mark plate 128 is fixed opposite to the mask-side reference mark plate 130. Movement of the carriage 112 in the direction of arrow A, causes mask 113 and plate 114 to be scanned by an illuminating system 117 and a projection optical system 118. A pattern is formed through mask 113 via illuminating light from illuminating system 117. To expose plate 114, the light that passes through mask 113 and which passes through projection optical system 118 becomes incident on plate 114. In FIG. 1, actuators 124a-124c control the position of the mask table during mask setup processes to ensure proper exposure.
The exposure device depicted in FIG. 1 is further illustrated in and discussed with regard to FIG. 2 which also is attached hereto. In particular, the projection optical system shown in FIG. 1 is made up of seven optical modules 1251-1257. Each optical module 125 has a trapezoidal exposure field that divides the pattern on mask 113 to be copied/projected onto plate 114. Each optical module 125 has a mechanism 126 to adjust the position of the projected image. The trapezoidal regions PA1-PA4 are projected by optical modules 1251-1254 while trapezoidal regions PA5-PA7 are projected by optical modules 1255-1257.
The trapezoidal regions are aligned in a direction (non-scanning direction) perpendicular to the scanning direction at a predetermined spacing. The ends (those portions shown by dashed lines in FIG. 3, which is attached hereto) of adjacent trapezoidal regions (for example, PA1 and PA5, PA5 and PA2, etc.), and the optical modules 1251-1257 are arranged such that they overlap by a predetermined amount in a non-scanning direction.
In mask-side reference mark plate 130, and in plate-side reference mark plate 128, as shown in FIG. 3, mask-side reference marks M1-M8, and plate-side reference marks P1-P8, are disposed such that the associated marks overlap. Such marks are located so as to correspond to the aforementioned overlap portions of the trapezoidal regions.
Calibration of the optical modules 1251-1257 is illustrated with regard FIG. 4, which also is attached hereto. As shown in FIG. 4, mask-side reference marks M1-M8 are projected onto plate-side reference marks P1-P8 via optical modules 1251-1257. Because reference marks M1-M8 and P1-P8 are formed and disposed to overlap, when the same do not overlap (e.g., because of device movement or drive anomalies, etc.), the optical modules are considered to be the cause of such an anomaly and any resultant distortion. Consequently, the relative positions of the marks M1, M2 projected by optical module 1251, and the plate-side reference marks P1, P2, are photoelectrically detected by use of a sensor 132 (e.g., a TV camera, etc.). In turn, positional displacement data (dx1, dy1) between mark P1 and the projected image of mark M1, and positional displacement data (dx2, dy2) between mark P2 and the projected image of mark M2 may be found and derived. With such displacement data (e.g., displacement measurement data, etc.), the particular adjustment mechanism 126 corresponding to optical module 1251 may be used to adjust optical module 1251 so that the respective positional displacement amounts become zero or tolerable.
Similarly, adjustment is performed relative to optical modules 1252-1257 such that corresponding mask-side reference marks (M3-M8) and plate-side reference marks (P3-P8) overlap. Furthermore, the adjustment of the optical modules 1255, 1256, 1257 may be performed by moving carriage 112, so that the reference marks enter the exposure fields of the optical modules 1255, 1256, 1257. Accordingly, adjustment is possible so that the seven optical modules are able to project the pattern on mask 113 accurately and within expected tolerances.
Although, prior exposure devices allow calibration of projected images and, in particular, calibration of projection optical systems to effect accurately projected design patterns, such calibration is performed by using mask-side reference marks disposed on a special mask-side reference mark plate which may be independent of the mask that is to be imaged and plate-side reference marks disposed on a special plate-side reference mark plate. Thus, in the case where there is a positioning error (due to a mask pattern error as shown by the solid lines in FIG. 5, for example), the same cannot be corrected by prior exposure devices. That is, because prior exposure devices are centrally concerned with registration and calibration of reference marks, they do not adequately address the problems associated with design pattern errors that are often realized. As such, design patterns like those shown in FIG. 5 often have been erroneously projected and imaged onto a plate or substrate. And, in particular, the positional errors that can result (especially for large masks) can approach xc2x11 xcexcm.
Thus, there exists a need to provide new and improved exposure devices and methods for making and using the same. Such devices must allow masks and reference marks to be integrally formed so that pattern and projection errors are minimized and avoided, and so that resultant exposures more accurately adhere to design requirements. To be viable, such devices and methods must allow projection exposures on substrates without realizing errors often associated with prior exposure devices.
The present invention has as its principal object to solve the aforementioned problems associated with prior image exposure devices by providing improved devices that deliver greater exposure accuracy and apparatus efficiency. Such improved devices will, in turn, allow manufacturers of liquid crystal display (LCD) panels, semiconductor elements, etc. to produce such components more accurately and reliably.
It is another object of the present invention to provide an exposure apparatus for use in a stepper unit that allows accurate imaging to be realized relative to a mask that may contain design pattern errors and the like.
It is still another object of the present invention to provide an exposure apparatus for use in a stepper unit that accommodates masks having integrally formed patterns and reference marks to facilitate accurate adjustment of corresponding projection optical systems.
It is a further object of the present invention to provide an exposure apparatus for use in a stepper unit that adjusts optical characteristics of imaging systems by utilizing reference marks that closely relate to attributes of a design pattern formed on a projection mask or reticle.
It is a further object of the present invention to provide an exposure apparatus that may be applied to many different types of stepper units including mirror-type units without causing significant increases in stepper size.
It is another object of the present invention to provide methods for making and using an exposure apparatus in accordance with the present invention.
By providing an exposure apparatus and related methods for making and using the same, certain benefits are realized. For example, an exposure apparatus according to the present invention will accommodate a mask or reticle that includes a design pattern which is integrally formed with related reference marks to be used to calibrate image exposure systems within a stepper unit. The present invention will allow masks (or reticles) to be used to reliably produce liquid crystal display (LCD) panels, for example, even when such masks contain design pattern errors and the like. And, an exposure apparatus according to the present invention will more accurately and efficiently respond to error conditions associated with design pattern errors and the like as automatic corrections may be made during exposure operations as opposed to realizing defective and unusable finished products. As such, more accurate imaging is made possible as reference marks formed on a mask allow an exposure apparatus according to the present invention to more closely respond to particularities of design patterns.
The present invention achieves the above-stated objects to deliver the aforementioned benefits by providing an exposure apparatus and methods for making and using the same. The exposure device includes at least one projection optical system that projects illuminating light, a substrate stage which supports a substrate to be exposed by the illuminating light and which includes a first plurality of reference marks. The exposure device also includes a mask stage which supports a mask including a mask pattern to be projected onto the substrate by at least one projection optical system. The mask further includes a second plurality of reference marks intended to correspond to the first plurality of reference marks. The second plurality of reference marks is integrally formed with the mask pattern. The projection optical system(s) project the illuminating light based on the mask pattern and the second plurality of reference marks to produce a projected image corresponding to the mask pattern and a plurality of projected images corresponding to the second plurality of reference marks. The exposure apparatus also includes an adjustment mechanism which adjusts the position of the projected image on the substrate based on a plurality of positional relationships between the plurality of projected images and the first plurality of reference marks. Also included is a plurality of sensors which detect the positional relationships, and a control device which controls the adjustment mechanism based on the positional relationships to effect a predetermined plurality of positional relationships between the plurality of projected images and the first plurality of reference marks.
According to another aspect of the present invention, provided is a method for making an exposure device. The method includes the steps of providing a projection optical system that is configured to project illuminating light, and providing a substrate stage that is configured to support a substrate to be exposed by said illuminating light. The substrate stage includes a first reference mark. The method further includes a step of providing a mask stage that is configured to support a mask including a mask pattern to be projected onto the substrate by the projection optical system. The mask further includes a second reference mark. The second reference mark is integrally formed with the mask pattern. The method further includes a step of configuring the projection optical system to project light to produce a projected image corresponding to the second reference mark. The projected image is to become incident on the substrate stage. The method also includes a step of providing an adjustment mechanism that is configured to adjust the position of the projected image on the substrate stage by adjusting the projection optical system based on a positional relationship between the projected image and the first reference mark. Finally, the method includes the steps of providing a sensor configured to detect the positional relationship, and providing a control device configured to control the adjustment mechanism based on the positional relationship to effect a predetermined positional relationship between the projected image and the first reference mark.
And, according to another aspect of the present invention, provided is a exposure method for exposing a mask pattern on a substrate via at least one projection optical system. The method includes the steps of arranging a first reference mark on a substrate stage that is configured to support a substrate to be exposed, and arranging a mask on a mask stage. The mask includes a design pattern and an integrally formed second reference mark. The method also includes steps of causing the first reference mark and the second reference mark to correspond, causing illuminating light to pass through the second reference mark to form a corresponding projected image on the substrate stage, determining a positional relationship between the projected image and the first reference mark, and adjusting the position of the projected image based on the positional relationship to effect a predetermined positional relationship between the projected image and the first reference mark. Finally, the method includes a step of exposing the substrate based on the mask pattern.